WASHINGTON — After leading the GOP primary in New Hampshire for most of the summer, former Massachusetts Gov. Mitt Romney's once significant lead over former New York City Mayor Rudy Giulianiand Sen. John McCainhas evaporated, according to the most recent polling. The fact that the Romney camp sent out a memo last week downplaying the significance of winning both Iowa and New Hampshire suggests his advisers are seeing the same thing.

But can a candidate who is counting on the momentum he gets from two early January wins to catapult him past his better-known GOP opponents really afford anything but total domination in the first two contests of '08?

Despite his low showing in national polling, the Romney camp has always counted on his ability to appeal to core primary voters to win the nomination. His heavy spending on both paid advertising and campaign staff helped him to jump out to early leads in both Iowa and New Hampshire. The rationale for this strategy is that without early wins, national front-runners like Giuliani and former Tennessee Sen. Fred Thompsonwould be left struggling for political oxygen. A one-two win would also make South Carolina, where Romney continues to trail even after much investment, less critical in his quest for the nomination.

If Romney were to lose New Hampshire, he'd then be forced to find a win in Michigan, South Carolina or Florida. A Michigan win is expected but not a given. A late August EPIC/MRA poll had Romney statistically tied with Giuliani. A loss in his home state would be a serious blow to Romney's campaign.

In South Carolina, according to Pollster.com trend analysis, Romney lags significantly behind Giuliani and Thompson. In Florida, Romney's trend line is moving up while Giuliani's has been trending down. Even so, he trails both Thompson and Giuliani.

It seems counterintuitive, but Romney actually needs Thompson in order to remain competitive. Sure, Thompson challenges Romney for the conservative mantle, but Thompson is also currently the most competitive with Giuliani in the South.

But as Thompson continues to struggle on the campaign trail, his ability to hold his lead in the southern states will likely begin to suffer.

If Thompson falters, Romney may also get some help from conservative leaders like Focus on the Family's James Dobson and the Family Research Council's Tony Perkins who have pledged to support a third-party candidate if Giuliani grabs the GOP nod. But will it matter? Do they actually campaign against Giuliani, or will they hope that their words are enough to discourage GOP primary voters? And if they don't ultimately embrace Romney, isn't he still vulnerable to attacks for his past positions on social issues? The success or failure of these conservative leaders to derail Giuliani will say as much about Giuliani's ability to weather the fallout as it does about their own political muscle.

What about McCain? Left for dead just a few weeks ago, the Arizona senator has seen his numbers rise in the last two New Hampshire polls. And he's leveled off in Florida and South Carolina polling after a precipitous drop through most of '07. Even so, while the focus has been on his fundraising woes, his problems are more fundamental than structural. Conservatives have always felt a strong reticence about McCain and it won't be healed simply because they are unhappy with the rest of the field. And the fact that McCain raised $5 million this quarter but is still holding $2 million worth of debt means that once the spending spree begins in New Hampshire, he won't be able to keep up. But he could have enough of an impact to keep Romney or Giuliani from a runaway victory.

Bottom line: The more muddled the early contests, the greater the Giuliani advantage. If the first primary/caucus states produce split decisions, the race for the nomination will be decided by the 20-plus states holding Feb. 5 primaries. No candidate can afford to compete in all of those states, which puts a premium on the candidate who is the best-defined nationally. That candidate, of course, is Giuliani.

Romney missed a chance to appeal to the base while also getting lots of national coverage by not jumping on the MoveOn.org controversy. Instead, Giuliani got there first and has made it his own. Romney can't expect to compete nationally if Giuliani continues to define the terms of the debate.